Escalators are provided with safety systems, each one of which is operable to stop movement of the escalator in the event that an unsafe operating condition is detected. Examples of such unsafe operating Conditions include: a missing step or a detached step on the escalator; a handrail which is moving at an improper speed; something becoming caught between adjacent steps or between the steps and the side skirts; a foreign object becoming lodged between the step treads and the combplate at the escalator exit landing; or the like. The safety system components used to detect unsafe escalator operating conditions include proximity sensors, switches, pressure sensors, or the like, which are able to detect unsafe escalator-operating conditions so long as the sensors and their associated circuitry remain operative. Present day escalators do not include any mechanism for determining the operability of the safety system detectors or their circuitry. It would be highly desirable to be able to detect safety circuit component failure prior to start up of the escalator. If a safety circuit component malfunction were detected, the escalator could be prevented from starting Up.